Across the globe there is great demand for disposable products including towel, sanitary tissue, and facial tissue. Important quality attributes of disposable sanitary tissue and facial tissue include softness and strength, while those of disposable towel include absorbency and strength. The various methods used to produce these products vary in their ability to generate these quality attributes.
Use of a structured fabric can deliver superior levels of bulk that improve absorbency and bulk softness of absorbent structures in disposable products. The higher the bulk and absorbency desired, the higher coarseness structured fabric that needs be utilized. A coarse fabric uses thick monofilament polymeric fibers to create deep valleys in the fabric for cellulosic or synthetic fibers (which compromise the absorbent structure) to penetrate and generate bulk. In structured fabrics made using topically applied and cured resin, an increased resin thickness is needed in order to obtain higher bulk. The downside of using these highly coarse or thick structured fabrics is that the surface smoothness will be negatively impacted. Further, when using TAD, UCTAD, ETAD, or the ATMOS (Twin Wire Configuration) methods (employing a structured fabric) to produce an absorbent structure, the fibers of the absorbent structure penetrate into the structured fabric through the application of vacuum pressure or as an effect of the speed differential between the absorbent structure and the structured fabric. These methods limit the maximum penetration depth and correspondingly, bulk that can be achieved. In an ATMOS process that utilizes a crescent former, the absorbent structure is formed directly between a wire and structured fabric, however, the structured fabric is placed in the inner position (with the structured fabric located between the absorbent structure and the forming roll) rather than the outer position (with the structured fabric located between the absorbent structure and the saveall pan). This means that the drainage of the absorbent structure occurs through the outer wire rather than the structured fabric. The centrifugal force around the forming roll forces water and fiber towards the outer wire limiting the fiber penetration into the structured fabric. Use of vacuum at the wet shaping box helps pull fibers deeper into the fabric, but the total penetration is much less than the void volume available in the fabric. A limitation of the NTT process is that the absorbent structure has to be pressed into the structured fabric which creates compaction that limits absorbency and softness potential.
There is a need in the art for a paper making machine whereby a web is pressed deeply into a structuring fabric in an efficient manner.